I replicated your results with your current sans-serif font. The case also occurred when I changed the font to monospace.

I believe you're better off using a non-system font. For instance, I wanted to see what would happen with a typical Google font such as Open Sans, and I found that the issue did not exist when using it.

By the way, good work on that website. It looks nice. TSM! TSM! TSM!

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